Unmanned aerial vehicles (UAVs) or drones have become increasingly popular in recent times. These drones can be controlled manually, or can fly autonomously according to a pre-programmed flight path. Because of these features, drones can be used in a variety of situations from work to recreation. For example, drones may be used to deliver objects from a warehouse to purchaser's residence. Drones may also be flown for fun such as in parks or backyards. Increasingly, drones are being flown in competitions, racing through predesigned courses.
Today's drones come with guidance systems that help them to know their location, altitude and trajectory. Various sensors and radios are used to detect the drone's height, speed, and current position. These sensors may be used to prevent the drone from flying into certain locations. For instance, drones may be prevented from flying near airports, stadiums or other locations where they may cause interference or harm. Such flight prevention boundaries are typically referred to as geofences. These geofence are stationary locations defined using global positioning system (GPS) coordinates. Upon reaching the boundary of a geofence, a drone's navigation system will stop it from flying beyond the walls of the geofence. In some cases, the drone may simply stop moving, and in other cases, the drone may be programmed to fly back to its launch location.